Non-pressure sight windows
Light-duty windows for vessels without excess pressure: threaded, clamp-mounted, on hatch covers.
What this is
Non-pressure windows are installed on silos, bunkers, storage tanks and process vessels where excess pressure and vacuum do not occur in any mode, including washing and filling.
A light-duty construction is cheaper than a pressure fitting, but its use on a pressure vessel is not allowed.
Verified characteristics
| Parameter | Value | Source |
|---|---|---|
| Mounting | special construction | Values without a confirmed source are not published on this site. |
| not specified | ||
Typical constructions
The composition of parts varies from construction to construction; the list below shows typical elements.
Threaded or clamp body
holds the glass and gasket pack.
Glass
often a borosilicate disc; the material follows the documentation.
Gasket
follows the medium and ambient conditions.
Cover or frame
presses the glass, often with quick replacement.
Mounting
Mounting is done by thread, clamp frame or on a hatch cover; torque and sealants (if allowed) follow the manufacturer instructions.
Limits of applicability
“Non-pressure” does not mean “any conditions”: medium heating, blocked vent lines or a technology change can create pressure. The limits are confirmed by the manufacturer of the specific product.
Do not use on pressure vessels and vacuum systems.
Verify washing modes and external heating.
Glasses
The glass material and thickness follow the construction; for replacement use discs with confirmed dimensions and material.
Dimensions
DN is usually not applied to non-pressure windows: the actual diameters of the glass and the connection are used instead.
Difference from pressure fittings
Pressure fittings (DIN 28120/28121) are designed for pressure and have confirmed assembly characteristics; non-pressure constructions do not provide such guarantees by default.
Frequent questions
Can a non-pressure window be installed on a reactor?
No — pressure vessels use pressure fittings with confirmed characteristics.
What if vacuum occurs in the vessel occasionally?
The presence of vacuum moves the selection into pressure categories; clarify the modes with the vessel designer.
Sources
- ACIopen the sourceTechnical review: 2026-11-04